The UK's greatness no longer comes from aircraft carriers and nukes and kicking ass around the globe. The country may have its problems but it's still an amazing place to live and work, with plenty of opportunity for those willing to look for it. This is precisely why so many people vote with their feet and still migrate to the UK.

In my view the best defense the UK could wish for is to be a thriving hub of commerce, humanity and culture, chock-full of people who'd be seriously pissed off if their prosperity was threatened. All the MoD needs is enough troops to maintain law and order, and warehouses full of pitchforks.